TY - THES

T1 - Influence of the beadless welding technology on the properties of PP-R and PVDF joints

AU - Brunbauer, Julia

N1 - embargoed until 06-09-2016

PY - 2011

Y1 - 2011

N2 - In this master thesis a beadless welding technology for polypropylene (PP) and poly(vinyliden) fluoride (PVDF) pipe systems of importance for pharmaceutical, biotechnological and life-science industry was tested. In the work the influence of welding parameters and of the welding machine on the material properties, on the mechanical strength and on the surface roughness of the joints was evaluated. Welding tests were performed with pipes and fittings with outer diameters (OD) 20 mm and 63 mm made of natural and grey coloured PP random copolymer (PP-R) as well as PVDF. The aim was to characterise the properties of the beadless welds produced with different welding parameters at 0 °C, 20 °C and 40 °C ambient temperature. Therefore, analytical tests such as melt flow rate (MFR), differential scanning calorimetry (DSC), oxidation induction time (OIT) and microtome sections were conducted. The mechanical properties of the joints were evaluated with tensile tests, bending tests, internal pressure creep rupture tests and tests to qualify the residual stresses in the joints. Beyond that the roughness of the inner joint surface was analysed with a confocal microscope. Subsequently, the results were compared to the features of heated tool butt and infrared joints. The investigations showed that the welding parameters took significant influence on the properties of the joints. Consequently, the parameters were optimised and adjusted to the different ambient temperatures. The determination of tolerance ranges for the welding parameters guaranteed good joint quality for the tested materials. Furthermore, the analytical tests proved that the material in the welding zone was not degraded during the welding process. The longer heating and cooling times compared to other welding methods even led to re-crystallisation and relaxation in the material. As a consequence, the residual stresses in the pipes decreased during the welding process. The residual stresses in beadless joints were even lower than in heated tool butt and infrared joints. The roughness of the inner joint surface was determined by the roughness of the inserted balloon. Due to the use of a certain balloon for each dimension, the welds OD 63 mm were less rough than the welds OD 20 mm. In all mechanical tests, joints made of pipes as well as fittings surpassed all requirements by far. The beadless joints reached even better results than the tested starting material.

AB - In this master thesis a beadless welding technology for polypropylene (PP) and poly(vinyliden) fluoride (PVDF) pipe systems of importance for pharmaceutical, biotechnological and life-science industry was tested. In the work the influence of welding parameters and of the welding machine on the material properties, on the mechanical strength and on the surface roughness of the joints was evaluated. Welding tests were performed with pipes and fittings with outer diameters (OD) 20 mm and 63 mm made of natural and grey coloured PP random copolymer (PP-R) as well as PVDF. The aim was to characterise the properties of the beadless welds produced with different welding parameters at 0 °C, 20 °C and 40 °C ambient temperature. Therefore, analytical tests such as melt flow rate (MFR), differential scanning calorimetry (DSC), oxidation induction time (OIT) and microtome sections were conducted. The mechanical properties of the joints were evaluated with tensile tests, bending tests, internal pressure creep rupture tests and tests to qualify the residual stresses in the joints. Beyond that the roughness of the inner joint surface was analysed with a confocal microscope. Subsequently, the results were compared to the features of heated tool butt and infrared joints. The investigations showed that the welding parameters took significant influence on the properties of the joints. Consequently, the parameters were optimised and adjusted to the different ambient temperatures. The determination of tolerance ranges for the welding parameters guaranteed good joint quality for the tested materials. Furthermore, the analytical tests proved that the material in the welding zone was not degraded during the welding process. The longer heating and cooling times compared to other welding methods even led to re-crystallisation and relaxation in the material. As a consequence, the residual stresses in the pipes decreased during the welding process. The residual stresses in beadless joints were even lower than in heated tool butt and infrared joints. The roughness of the inner joint surface was determined by the roughness of the inserted balloon. Due to the use of a certain balloon for each dimension, the welds OD 63 mm were less rough than the welds OD 20 mm. In all mechanical tests, joints made of pipes as well as fittings surpassed all requirements by far. The beadless joints reached even better results than the tested starting material.

KW - wulstlose Schweißung

KW - Rohrsysteme

KW - PVDF

KW - PP-R

KW - MFR

KW - DSC

KW - OIT

KW - Zugversuch

KW - Biegeversuch

KW - Zeitstandinnendruckversuch

KW - Rauheiten

KW - beadless welding process

KW - PVDF

KW - PP-R

KW - pipe systems

KW - MFR

KW - DSC

KW - OIT

KW - tensile tests

KW - beding tests

KW - internal pressure creep rupture tests

KW - roughness tests

M3 - Master's Thesis

ER -